YOU SAID:

Last night i was up until five in the morning because i was watching videos on my smart phone

INTO JAPANESE

昨夜、私はスマートフォンでビデオを見ていたので、午前中は5時までだった

BACK INTO ENGLISH

Last night I was watching videos on smartphone, so it was until 5 o'clock in the morning

INTO JAPANESE

昨夜、スマートフォンで動画を見ていたので、朝5時までだった

BACK INTO ENGLISH

Last night, I was watching videos with smartphone, so it was until 5 in the morning

INTO JAPANESE

昨夜、スマートフォンで動画を見ていたので、朝5時までだった

BACK INTO ENGLISH

Last night, I was watching videos with smartphone, so it was until 5 in the morning